18 May 2009 Automatic alignment system for optical lithography based on machine vision
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This paper presents an automatic alignment system based on machine vision method. A high-speed gray pattern match algorithms is proposed based on the combination of sequential similarity detection algorithm (SSDA) and multiresolution pagoda structure algorithm (MPSA). A dynamic system calibration model suitable for the algorithm automatic alignment system is established to relate the pixel coordinate in CCD to the physical coordinate, which is based on Tsai's two-step algorithm but with the help of precise positioning of the wafer stage in X-Y directions. A lot of experiments conducted on a machine vision experimental platform confirm that the proposed technique is feasible and effective. The pattern match algorithm is demonstrated to achieve an error less than one-twentieth pixels, while the computation time is shorter than 200ms when using a large pattern image with 320×320 pixels. The absolute alignment error is illustrated to be lower than 200nm within a large field of view of 1mm×1mm after the platform is calibrated using the proposed dynamic calibration method.
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Tao Huang, Tao Huang, Shiyuan Liu, Shiyuan Liu, Pengxing Yi, Pengxing Yi, Tielin Shi, Tielin Shi, } "Automatic alignment system for optical lithography based on machine vision", Proc. SPIE 7284, 4th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems, 72840I (18 May 2009); doi: 10.1117/12.832076; https://doi.org/10.1117/12.832076

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